Immobilized enzyme

About: Immobilized enzyme is a research topic. Over the lifetime, 15282 publications have been published within this topic receiving 401860 citations.

Oxidation of ABTS by hydrogen peroxide catalyzed by horseradish peroxidase encapsulated into sol–gel glass.: Effects of glass matrix on reactivity

Abstract: Encapsulation of horseradish peroxidase (HRP) by the sol–gel method into silica (SiO 2 ) or alkylated silica (RSiO 2 , in which R is Me or Pr) yields biocatalytic glasses designated HRP@SiO 2 and HRP@RSiO 2 . These new enzyme composite materials catalyze one-electron oxidation by H 2 O 2 of the dye 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) into the radical cation ABTS + . In the presence of excess H 2 O 2 , ABTS + is converted into a mixture of at least five compounds. This undesirable side-reaction can be suppressed by using stoichiometric amount of H 2 O 2 . The effects of ABTS concentration and ionic strength of the buffer on the ABTS + yield and the apparent rate constant were investigated. The catalyst HRP@MeSiO 2 achieves higher ABTS + yields (70–85%) than HRP@SiO 2 and HRP@PrSiO 2 (30–40%) do. The apparent rate constants for HRP@MeSiO 2 are 7–10 times higher than those for HRP@SiO 2 and HRP@PrSiO 2 . When the ionic strength of the buffer is raised, the rate constants increase for HRP@SiO 2 and HRP@PrSiO 2 , and do not change for HRP@MeSiO 2 . The diminished electrostatic interaction between the negatively-charged substrate, ABTS, and the surface of methylated silica is the main cause for the increased catalytic efficiency. These results are important for understanding of encapsulated and otherwise immobilized enzymes. The possible electrostatic effects should be taken into consideration in the choice of the matrix materials used in the design of biosensors, supported catalysts, and other composite materials.

Immobilization of lipases for non-aqueous synthesis

Abstract: Immobilization of lipases involves many levels of complications relating to the structure of the active site and its interactions with the immobilization support. Interaction of the so called hydrophobic ‘lid’ with the support has been reported to affect synthetic activity of an immobilized lipase. In this work we evaluate and compare the synthetic activity of lipases from different sources immobilized on different kinds of supports with varying hydrophobicity. Humicola lanuginosa lipase, Candida antarctica lipase B and Rhizomucor miehei lipase were physically adsorbed onto two types of hydrophobic carriers, namely hydrophilic carriers with conjugated hydrophobic ligands, and supports with base matrix hydrophobicity. The prepared immobilized enzymes were used for acylation of n -butanol with oleic acid as acyl donor in iso-octane with variable water content (0–2.8%, v/v) as reaction medium. Enzyme activity and effect of water on the activity of the immobilized derivatives were compared with those of respective soluble lipases and a commercial immobilized lipase Novozyme 435. Both R. miehei and H. lanuginosa immobilized lipases showed maximum activity at 1.39% (v/v) added water concentration. Sepabeads, a methacrylate based hydrophilic support with conjugated octadecyl chain showed highest immobilized esterification (synthetic) activity for all three enzymes, and of the three R. miehei lipase displayed maximum esterification activity comparable to the commercial enzyme.